1. Field of the Invention
The invention relates to a dilute copper alloy material which has high productivity and is excellent in conductivity, softening temperature and surface quality, a dilute copper alloy wire, a dilute copper alloy twisted wire and a cable using the same, a coaxial cable and a composite cable, and a method of manufacturing the dilute copper alloy material and the dilute copper alloy wire.
2. Description of the Related Art
In recent industrial products such as electronic devices and vehicles, a copper wire is often used harshly. In order to address these needs, a dilute copper alloy material which can be manufactured by a continuous casting and rolling method, etc., and has productivity higher than that of pure copper while maintaining conductivity and elongation characteristics to a pure copper level has been being developed.
A dilute copper alloy material is demanded to be a soft conductor having conductivity of 98% or more, or further, 102% or more as a general purpose soft copper wire or a copper material to which the softness is required, and the intended purpose thereof includes a cabling material for consumer solar cell, an enameled wire conductor for motor, a high-temperature application soft copper material used at from 200° C. to 700° C., a molten solder plating material not requiring annealing, a copper material excellent in thermal conductivity and a material alternative to high purity copper, which addresses a wide range of these needs.
A technique of controlling oxygen in copper to 10 mass ppm or less is applied to a base in the raw material as the dilute copper alloy material, and it is expected to obtain a dilute copper alloy material having high productivity and excellent in conductivity, softening temperature and surface quality by adding a small amount of metal such as Ti to copper atoms in the base, and then, melting and solidifying in the form of atom.
As described in a of “Iron and Steel” by Hisashi Suzuki and Mikihiro Sugano (1984), No. 15, 1977-1983 regarding conventional softening, the result has been obtained in which the softening of a sample in which 4-28 mol ppm of Ti is added to electrolyte copper (99.996 mass % or more) occurs earlier than a sample without addition. The non-patent literary document has concluded that this is caused by a decrease in solid solubility S due to formation of sulfide of Ti.
JP-B-3050554, JP-B-2737954 and JP-B-2737965 have proposed to continuously casting in a continuous casting apparatus using a dilute copper alloy in which a small amount of Ti is added to oxygen-free copper, which have been already patented.
Here, a method of reducing oxygen by a continuous casting and rolling method is also known as described JP-B-3552043 and JP-B-3651386.
JP-A-2006-274384 proposes that, when a copper material is manufactured directly from molten copper (or copper melt) by the continuous casting and rolling method, the softening temperature is lowered by adding a small amount of metal such as Ti, Zr or V (0.0007-0.005 mass %) to the molten copper with an oxygen amount of 0.005 mass % or less. However, in JP-A-2006-274384, conductivity is not examined and a range of manufacturing conditions for achieving both of the conductivity and the softening temperature is unclear.
On the other hand, JP-A-2008-255417 proposes a method of manufacturing an oxygen-free copper material having a low softening temperature and high conductivity, in which a copper material is manufactured by a drawing-up continuous casting apparatus using molten copper in which a small amount of metal such as Ti, Zr or V (0.0007-0.005 mass %) is added to the oxygen-free copper with an oxygen amount of 0.0001 mass %.
However, a material including a small amount of oxygen, i.e., including oxygen at a concentration of ppm order similarly to the dilute copper alloy material as described above, is not examined in any patent documents as well as the non-patent literary document.
Therefore, a practical dilute copper alloy wire having high productivity and excellent in conductivity, softening temperature and surface quality as well as a composition thereof have been desired to be examined.
In addition, as for the examination of the manufacturing method, a method of softening copper by adding Ti to oxygen-free copper by continuous casting is known as described above, in which a wire rod is made by hot extrusion or hot rolling after manufacturing a casting material as cake or billet. Thus, the manufacturing cost is high and there is a problem of economic efficiency for industrial use.
In addition, although a method of adding Ti to oxygen-free copper by the drawing-up continuous casting apparatus is known, there is also a problem of economic efficiency due to the slow production rate.
Then, a method using a SCR continuous casting and rolling system (South Continuous Rod System) is examined.
In a SCR continuous casting and rolling method, molten metal is formed by melting a base material in a melting furnace of the SCR continuous casting and rolling apparatus, desired metal is added to and melted in the molten metal, a roughly drawn wire (e.g., 8 mm in diameter) is made of the molten metal, and the roughly drawn wire is drawn to be, e.g., 2.6 mm in diameter by hot rolling. Also, it is possible to be processed into a wire with a diameter of 2.6 mm or less, or a plate material or a deformed material in the same way. In addition, it is effective to roll a round wire rod into a rectangular or contour strip. Alternatively, it is possible to make a deformed material by conform extrusion of casting material.
As a result of the examination by inventors, etc., it is found that a surface flaw is likely to be generated in tough pitch copper as a base material when the SCR continuous casting and rolling is used, and variation of softening temperature and a status of titanium oxide formation are unstable depending on conditions for addition.
In addition, when examined using oxygen-free copper of 0.0001 mass % or less, the conditions which satisfy the softening temperature, the conductivity and the surface quality are in a very narrow range. Furthermore, there is a limit to decrease the softening temperature, thus, the further lower softening temperature which is equivalent to that of high purity copper is desired.